High frequency drying of separate pieces



March 4, 1969 w. N. BENNETT HIGH FREQUENCY-'DRYING OF' SEPARATE PIECESl Filed April 18. 1967 United States Patent O 3,430,350 HIGH FREQUENCY DRYING F SEPARATE PIECES William N. Bennett, South Miami, Fla., assignor to Fitchburg Paper Company, Fitchburg, Mass., a corporation of Delaware Filed Apr. 18, 1967, Ser. No. 631,819 U.S. Cl. 34-1 12 Claims Int. Cl. F26b 3/34, 11/06; B01k 3/02 ABSTRACT 0F THE DISCLOSURE This invention s directed to the uniform drying by high frequency electric tields of segmental or discrete length materials. To prevent the normal field `defects at the material ends, the electrodes which apply the field, are mounted upon a turntable which is rotated in parallel with the material which is held stationary or slowly moved in the established field. Alternatively, the field may be electrically rotated. In each case the field is uniformly applied to the material body as well as its ends.

BACKGROUND OF THE INVENTION Field of the invention The invention is applicable to the drying or curing of materials in segmental or discrete lengths which are to be dried or cured with a uniform moisture profile or degree of curing, both in the body of the materials and at its ends.

Description ofthe prior art 'In prior art high frequency drying devices, materials in continuous web form were handled. Little use of such devices was made for segmental or discrete length materials because of the lack of uniform field obtained at the ends which caused less drying at the ends and this prevented a uniform moisture profile. Thus, segmental or discrete length items were dried or treated in other types of drying devices.

Summary of the invention High frequency electric fields have proved very successful for the quick and even drying of materials passing through such fields in web form, but there are instances where it is desirable to increase the speed of the drying processes by the use of high frequency electric fields where the materials do not lend themselves to being dried in the form of a web. As examples, there are builders boards such as Masonite, asbestos board and the like, and hides of leather pasted to a surface, which dry slowly and are substantially rigid or supported rigidly and cannot be arranged in web form for one reason or another.

One of the diliiculties encountered in the use of high frequency electric drying of materials in discrete lengths is caused by the use of stationary flux field generating electrodes. lf a segmental or discrete length type of material is passed over the stationary electrodes power input to the material is not evenly distributed over the entire material due to the loss of field continuity in the immediate area of the leading or entering edge of the material and also in the trailing or back edge. In other words, the resistivity of a materials front and back edges is not as great when presented to the stray electromagnetic liux field as it is in the area between these two edges. If electrode spacing were, e.g., four inches apart, the leading and trailing edges of the material would receive very little power input within approximately four inches of each edge, whereas the remainder of the segmental or Patented Mar. 4, 1969 ice discrete length material would receive full power input and dry faster.

If the material was stationary over stationary electrodes, the power input would be concentrated between the electrodes, with little or no power input directly above the electrodes themselves.

=On the other hand, if the material is oscillated back and forth over the stationary electrodes, the same thing would happen as if the material was conveyed over the electrodes.

This invention provides means for the high frequency drying of such segmental or discrete length materials and it includes the provision of a series of alternate energized and grounded electrodes which are arranged on a rotary or oscillatory head and are moved during the drying period with the material being dried located in the field produced by said rotating or oscillating electrodes. By ythis means, all portions of the material being dried, are evenly and uniformly dried for the reason that the electrodes are movably associated with respect to the fixed length of material.

Other objects and advantages of the invention will appear hereinafter.

Brief description of the drawings Reference is to be had to the accompanying drawings in which:

FIG. 1 is a view in side elevation illustrating in diagrammatic form the machine according to the present invention.

FIG. 2 is a view in front elevation looking in the direction of arrow 2 in FIG. l, with parts omitted.

FIG. 3 is a section through the baring and the rotary coupling, and

FIG. 4 is a view similar to FIG. 2 showing a modification on a reduced scale.

Referring now to the drawings, the reference numeral 10 indicates a high frequency generator cabinet, the generator itself being well known in the art as is the transformer which can be located either here or at a distance. The usual controls, etc., are provided but not shown aS these are well known.

In the case at hand, a rotary bearing indicated at 12 is provided through which the energizing connection to be hereinafter described extends from the generator cabinet 10 to a variable capacitor 14 and thence to the plate 16 mounting the elongated electrodes 18, 18 for energization thereof. Alternating with the electrodes 18 are the grounded electrodes 20 and it will be apparent that the electromagnetic field extends to the right of these electrodes in such a way as to pass to the workpiece W.

A drum type of support or the like at 22 in bearing 12 is driven slowly by a motor. The framework 24 holding the electrodes is mounted on the drurn 22 and rotates therewith.

The workpiece W is a relatively stiff or substantially self-sustaining board type of material which is to be dried and it is moved into place by any means either manual or by power on. the rollers at 26. When it is placed in the area of the field, it is stopped and it will be apparent that due to the rotary motion of the electrodes, all surfaces of the workpiece W will be equally affected by the high frequency field.

Materials such as hides of leather may be pasted upon a stiff dielectric material and passed through the field in the same manner.

In addition to holding the work stationary, as mentioned, it can be moved slowly past the rotary field for continued production. The speed of travel by the electrodes would be goverened by the power required to complete the necessary moisture removal from the workpiece W. The spacing between the electrodes and the workpiece W governs the degree of power input required.

The drying can also be carried out by passing the separate workpieces horizontally through the high frequency field with the air of conveyors or carrying belts. The proximity of the material to be heated r dried to that of the electrodes is critical and control of power input with respect to the variable capacitance created by this same distance and movement is imperative.

Any kind of supports or the like can be utilized to hold the workpiece vertical in the correct position and any means desired can be used to move it out of the drying area when it is dried to the degree desired.

Also, of course, the entire apparatus may be placed on its side so that the field is rotated on a vertical axis rather than on a horizontal axis and simple means may be utilized for supporting the sheet or piece to be dried either under it or over it, depending upon the situation found most convenient for the construction and operation of the device.

Additionally, the electrodes may be held stationary and the field rotated or oscillated by energizing the electrodes in a sequential pattern employing a distributor or commutator. The workpiece may be stationary or moving and the entire unit may be vertical or horizontal as was described above,

In FIG. 3 there is shown the energized rod at 30 which derives its energy from the high frequency generator in the cabinet and it may have a collar or the like as at 32 mating with a rod 34 which leads directly to the capacitor 14. The coupling 32 is conveniently made as a rotary coupling so that the rod 30 need not rotate but the rod 34 does rotate with the framework at 24 while the power is passed through the rods 30 and 34 to the capacitor as will be clear to those skilled in the art.

The applicator or electrodes may be square as shown in FIG. 2 or round as shown in FIG. 4. If the square is used the maximum workpiece should be of a size shown in dotted lines X. The working area should not exceed the outside rotational dimension of the hot (shorter) rods, but with the rotary or oscillatory head, some segmented workpeces can be passed slowly and continuously past the electrodes.

Having thus described my invention and the advantages thereof, I do not wish to be limited to the details herein disclosed, otherwise than as set forth in the claims, but what I claim is:

1. A method 0f drying: comprising (a) providing a high frequency field from a series of spaced electrodes disposed in a predetermined pattern and plane;

(b) exposing material to be dried to said high frequency field; and

(c) providing relative movement between said field and said material while said material is exposed to said field.

2. The method of drying of claim 1 wherein the relative movement is rotary.

3. The method of drying of claim 1 wherein the relative motion is rotary and about an axis at right angles with a plane parallel to at least one surface of the material being dried.

4. The method of drying of claim 1 wherein the material to be dried is held stationary and the high frequency electric eld is rotated with respect thereto.

5. The method of drying of claim 1 wherein the material to be dried is in sheet form.

6. A drying apparatus: comprising (a) a series of spaced electrodes;

(b) energizing means for energizing said electrodes to provide a high frequency field;

(c) support means adapted to position material for exposure to said high frequency electric field; and

(d) means for providing relative movement between said high frequency electric field and the material when disposed therewithin.

7. The drying apparatus of claim 6 wherein the high frequency eld is moved.

8. The drying apparatus of claim 7 wherein said means for providing relative movement rotates said electrodes about an axis of rotation normal to a predetermined plane.

9. The drying apparatus of claim 8 including means for supporting the material to be dried with at least a surface thereof in a plane normal to the axis of rotation of said electrodes.

10. An apparatus for drying an article of material in substantially fiat sheet form: comprising (a) a series of alternately disposed grounded and energizable electrodes disposed substantially in a coplanar relationship;

(b) article locating means for the supporting and locating an article in proximity to and parallel with the plane of said electrodes; and

(c) moving means for moving said electrodes in their own plane and relative to said article.

11. The apparatus of claim 10` wherein said moving means rotates said electrodes in their own plane,

12. The apparatus of claim 10 wherein said moving means rotates said electrodes in their own plane and about an axis normal to at least one surface of the article.

References Cited UNITED STATES PATENTS 2,147,689 2/1939 Chalee 34-1 JOHN I. CAMBY, Primary Examiner.

U.S. Cl. X.R.

Notice of Adverse Decision in Interference In Interference No. 98,417 involving Patent No. 3,430,350, W. N. Bennett, HIGH FREQUENCY DRYIN G OF SEPARATE PIECES, final judgment adverse to the patentee was rendered Mar. 29, 1974, as to claims 1, 5, 6 and 7,

[Oficial Gazette July 2, 1.974.] 

